Method and apparatus for operating an engine-driven chain saw in an environment where ice may form in the carburetor of the engine

ABSTRACT

An improved chain saw and method of operating a chain saw in a cold, humid environment where ice may form in the carburetor of the chain saw engine is disclosed. An ice-inhibiting substance is mixed with the fuel and lubricating fluid and introduced into an interior portion of the carburetor in conjunction with the combustible mixture of fuel, lubricating fluid, and air during operation of the two-cycle internal combustion chain saw engine in order to inhibit the formation of ice therein. The ice inhibiting means may be premixed with the lubricating fluid.

ilmted States Patent 11 1 1111 3,881A52 Dilworth et al. 1 1 May 6, 1975[54l METHOD AND APPARATUS FOR 3.067J38 12/1962 Johan ct ul. 44/58 XOPERATING AN ENG|NE DRWEN CHMN 3.230.057 1/1966 Sieker 44/58 SAW N ANENVRONMENT WHERE CE :xggg IN THE CARBURETOR OF THE 3,498,280 3/1970Zimmerer et ul. 123/122 R l v t J h L i D h S t M FOREIGN PATENTS ORAPPLICATIONS n en ms: 0 n ews wor an a on1ca' 753,622 2/1967 Canudu44/58 ,zlmmere" 423.510 2/1935 United Kingdom 123/1911 A both of Cahf.1731 Assignee: McCulloch Corporation, Los Primary Examiner-Charles J.Myhre Angeles. Calif. Assistant Examiner-R. H. Lazarus [22] Filed: Jan.22 973 $232215 Agent, or Firm-Burns, Doane, Swecker &

[21] Appl. No.: 325,346

[57] ABSTRACT U.S. Cl. An improved chain saw and method of perating aIn. CL t chain aw in a Id environment wherg ice 1 Field Search 193 A mayform in the carburetor of the chain saw engine is 44/53 disclosed. Anice-inhibiting substance is mixed with the fuel and lubricating fluidand introduced into an 1 Rem'mces cued interior portion of thecarburetor in conjunction with UNITED STATES PATENTS the combustiblemixture of fuel, lubricating fluid. and 2307526 9/1957 Foreman 44/53 Xair during operation of the two-cycle internal combus- 2.843.463 7/1958Gaston e1 n1 44 53 tion chain saw engine in order to inhibit theformation 2.844.448 7/1958 Heislcr ct a1 44/58 X of ice therein. The iceinhibiting means may be pre- 2,876,750 3/1959 Carr 123/1 A mixed withthe lubricating fluid. 2,883,276 4/1959 Larsen i23/l A X 2.896.5937/1959 Riemenschneider 123/1 A 1 Claim 3 Drawing Figures 1 METHOD ANDAPPARATUS FOR OPERATING AN ENGINE-DRIVEN CHAIN SAW IN AN ENVIRONMENTWHERE ICE MAY FORM IN THE CARBURETOR OF THE ENGINE BACKGROUND OF THEINVENTION This invention relates generally to a novel method andapparatus for operating a chain saw in a relatively cold environment.More particularly. this invention provides a chain saw including an iceinhibitor which substantially inhibits the formation of ice in theinternal portion of a carburetor of the two-cycle engine of the chainsaw to substantially prevent carburetor blockage during operation of theengine in cold. humid atmmospheric conditions.

Because of the substantial increase in the use of gasoline engines ofthe two-cycle type for chain saws by the general public and by thelogging and lumber industry. satisfactory. trouble-free engineperformance is extremely desirable in the operation of such engines.Two-cycle chain saw engines giving dependable performance can bemanufactured in small sizes. making their use ideal forv service inremote regions of the world wherein large scale logging operations havebegun to take place.

in the operation of gasoline engines of the two-cycle type. alubricating oil-gasoline motor fuel mixture which not only functions asa fuel. but also provides lubricatin in a highly diluted form withoutthe sump-type or crankcase lubrication system. is utilized. Many chainsaw operators use special chain saw lubricating oil for this purpose.Moreover. manufacturers may provide chain saw lubricating oil incontainerscorresponding to the volume of the fuel reservoir tofacilitate mixing the proper ratio of gasoline and lubricant.

When internal combustion engines of the type noted are operated in cold(approximately 40F to sub freezing. temperatures). humid (approximately50-100! relative humidity). weather. or in a cold humid environmentimmediately surrounding the cngine. a stalling problem may beencountered. it has generally been recognizcd that repeated enginestall- 2 over. the stalling of a chain saw engine in the mid: felling atree may impose a serious safety hazard wl precise timing is critical tocontrol of the fall.

A variety of methods and apparatus presently i for heating thecarburetor of a chain saw engine to prove operation under relativelycold weather co tions. For example. a closed circuit. radiatomypc ingsunder such cold. humid conditionsmay be caused Y by a formation of icein the carburetor. The accumulation of this ice produces a blockage inthe carburetor. most generally in the vicinity of the throttle. and mayseriously interfere with the production of a fuel-air mixture suitablefor combustion in-the cylinder of the engine. it is known that gasolineevaporating in the carburetor has a sufficient refrigerating effect tocondense and freeze the moisture present in air even intemperaturessomewhat above the freezing temperature. As a result. iceparticles may deposit along the interiorof the carburetor. and as notedabove. partially or completely block the air passage between thecarburetor wall and the carburetor throttle valve with a resultingstalling. This stalling may be particularly pronounced when the chainsaw engine is idling.

As noted above. the chain saw art has advanced to the state where manylumbering operations are conducted with internal combustionengine-operated. portable chain saws. M any of these logging operationstake place in extremely cold or snowy climates. and excessive enginestalling as a result of ice formation in the carburetor may be a sourceof serious annoyance and expense with a resulting increased fuelconsumption. inconvenience and delay of frequent restarting. Moretem.which has been found to be particularly effer for preheating the airwhich is passed to the carbur air inlet of the engine. is disclosed ina'U.S. Zimm et al. Pat. No. 3.498.280. in addition. a method ill".paratus for utilizing a stream of exhaust gas. whit generated by a chainsaw engine. by directing stream. as a free flow. through air towards aPI lected location on 'a chain saw is disclosed in a Loop Pat. No.3.678.973.

While these prior concepts are individually un and advantageous. therehas remained a need for 1 tional techniques which would be operable tofacil the operation of chain saws under cold weather Ct tions. Sincecompactness and simplicity have bec some of the primary characteristicsof modern chain saws. it has become desirable. in coping icingtendencies. to provide a solution to such problems without engenderingstructural compl and added fabrication costs.

it is. therefore. a general object of the present it tion to provide amethod and apparatus for inhil the formation-of .ice in the caiburetorof 'a two-l chain saw enginewhich minimizes or reduces the lems andlimitations previously existing in the prio his a more particular objectto provide a methl operation of a two-cycle chain saw engine whic eludesthe use of an ice inhibitor'to substantially vent the formmation of iceinside a carburetor of a cycle chain saw engine.

it is also an object of the present invention to pr an engine for achain saw and other devices whicl be operated in a cold. humid orsnowyenviron without an external carburetor heating means to ll the formationof ice in the carburetor thereof.

Another object of the present invention is to pr a method of inhibitingthe formation of ice in th buretor of a two cycle chain saw engine whichor may be employed without requiring modification conventional chain sawstructure.

An additional object of the present invention provide a method whichminimizes trouble to a saw operator whereby an ice inhibitor may beducedinside the carburetor of an engine for a saw or. say. a snowmobileduring operation of ti gine bymeans of an additive premixed with theeating oil. for the engine. which ice inhibitor su tially prevents theformation of ice in the carbun an amount sufficient to induce stallingof the en A method and apparatus for inhibiting the for: of ice in atwo-cycle chain saw engine accordin preferred embodiment of the presentinventi tended to accomplish at least some of the foregoi jects includesa chain saw having a frame. a cut connected to the frame. a cuttingchain trained i the outside of the cutter bar. and a two-cycle n eatingpiston internal combustion engine conne the frame for selectivelydriving the cutting cl will. of course. be appreciated that a rotary pisgine could be used in the practice of this lilVClillt internalcombustion engine has a carburetor in an interior portion comprising aninduction passage. :1 throttle valve. a venturi throat which is definedby a portion of the induction passage and the throttle valve. and achoke plate. An ice inhibiting means is mixed with the fuel andlubricating fluid and introduced into the interior portion of thecarburetor in which ice may form in conjunction with the combustiblemixture of fuel. lubricating fluid and air. That is to say. during theoperation of the engine. the ice inhibiting means is carried through thecarburetor with the combustible mixture. As the mixture passes throughthecarburetor. ice is substantially prevented from forming within theinterior of the carburetor. By introducing the ice inhibitor into theinterior of the carburetor in such a manner to prevent the ice fromforming. blockage of the carburetor from ice deposits is substantiallyprevented. An ice inhibiting means intended to accomplish at least someof the foregoing results may include. but is not limited to. hexyleneglycol (i.e.. 4-methyI-2.4-pentanedioll.

Other objects and advantages of the present invention will becomeapparent with reference to the following detailed description of apreferred embodiment thereof in connection with the accompanyingdrawings. in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a partial sectional view ofa chain saw according to the present invention:

FIG. 2 is a schematic sectional view of the carburetor of the chain sawof FIG. I wherein an ice inhibiting means has been introduced; and

FIG. 3 is a schematic sectional view of a carburetor in the prior artwherein deposits of ice have accumulated to block flow through thecarburetor.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTIONReferring now to the drawings. wherein like refer ence characters havebeen applied to like parts throughout. in FIG. I there is illustrated achain saw having a guide bar I2 supporting a cutter chain I4. A handle16 provides a triggertype. throttle lever 18. A two-cycle. internalcombustion engine 20 serves to impart power to the cutter chain I4 so asto cause the chain 14 to traverse or train around the periphery of theguide bar 12. A drive connection interposed between the engine and thecutter chain may include a conventional. pull-type starter.Alternatively. an electrical self-starting system (not shown) may beprovided.

In any event. this structure is now well known in the chain saw art. Itcorresponds. in general. for example. to the basic structure describedin a publicly available McCulloch Shop Manual associated with the Mac[-10 and 2-l0 chain saw manufactured by the McCulloch Corporation. LosAngeles. Calif.

The chain saw may further include a fuel tank 22. and an engine mountingbracket 24. The bracket may comprise an integral portion of a casting ormay be a molded portion ofa fuel tank 25. An upper portion 26 of thechain saw 10 comprises an enclosure 28. The enclosure 28 provides acarburetor housing cavity 30. the lower end portions of which aredefined by enclosure walls 34.

A conventional carburetor 36 is positioned in the cavity and is disposedin air flow transmitting communication with an inlet passage 38 in a nowwellknown manner.

An upper portion 40 of the carburetor 36 contains a conventional opening42 leading to an air transmitting or carburetor induction passage 44.

The carburetor 36 is secured to the engine 20 with the induction passage44 connected to an engine inlet 56 which communicates with the crankcaseof the engine 20. The upper portion of the cavity 30 may be closed by apreformed. foraminous air filter 46.

Turning now to FIG. 2. there is schematically depicted the carburetor 36of the engine 20 illustrated in the chain saw I0 of FIG. I. Thecarburetor 36 includes a carburetor body 48. having an induction passage44 therethrough which includes an air inlet portion 50 and a mixtureoutlet portion 52 with a venturi 54 interposed therebetween andconnecting the passage portions 50.52. By having the diameter of theinlet portion 50 the same as that of the outlet portion 52. improvedoperation may be obtained.

The flow of fluid through the induction passage 44 is controlled bymeans of a throttle plate or valve of the butterfly type. which ismounted on a throttle shaft 62.

Means for providing a suitably rich mixture for cold starting and warmup is provided by a butterfly type of choke plate or valve 64 which ismounted on the shaft 66. Means are also provided by idle fuel jet 65 forsup plying fuel to the carburetor when the engine is idling. The chokevalve 64 is disposed in the air inlet portion 50 of the inductionpassage 44 and may be of the same diameter as the throttle valve 60. Anysuitable wellknown means may be used for rotating the choke valve shaft66 so that the choke valve will be moved to a closed or open orintermediate position.

These components thus far described are now well known. There will nowbe described a unique concept for inhibiting the formation of ice in thecarburetor. As noted above. carburetor icing has continued to be aproblem in the operation of chain saws utilizing twocycle internalcombustion engines where the chain saw is operated in a relatively coldand humid environment. When the chain saw I0 is operated in such a cold.humid environment without provision for anti-icing. ice 67 mayaccumulate within the interior portion of the carburetor andparticularly may accumulate on the throttle plate 60 as shown in FIG. 3.Many icing problems occur when the throttle plate 60 is in or near theclosed or idle position. Under these conditions. little. if any. fuel isdischarged by the main jet (not shown) of the carburetor. During idlingof the engine. ice formation may occur. above. below and in the smallopening between the throttle plate 60 and the carburetor wall. Inaddition. any ice which does accumulate on the throttle plate when it isopen tends to obstruct the idle air flow when the throttle is closed.Hence this accumulation may be sufficient to appreciably block the flowof combustible fuel mixture through the carburetor with a result inrough engine operation and stalling.

The present invention functions to inhibit ice formation in the internalportion of the carburetor I0 and thereby substantially prevents icecrystals from accumulating on the induction passage surfaces to form ablockage.

As shown in FIG. 3. in the absence of the ice inhibiting means of thepresent invention. ice will generally form on edges 68 of the throttleplate 60 and can spread progressively across the plate face 70.Simultaneously. ice may accumulate along the walls of the inductionpassage 44. especially while the engine is idling. when an increasedfluid flow around the throttle may enhance the evaporation of gasolineand. hence. may produce an increased refrigerating effect. Without theuse of anti-icing devices. ice formation may accumulate both on thethrottle plate 60 and along the side walls of the carburetor in such amanner as to restrict the flow of combustible mixture. Such arestriction may result in engine stalling or rough operation. and thechain saw will often fail to perform until the blockage is removed.

While there is no intention to be bound by theoretical considerations.it appears that the ice inhibitor may lower the freezing point of waterin the internal portions of the carburetor to a temperature below thatwhich would ordinarily occur in the carburetor of a two-cycle chain sawengine operating in a cold. humid environment. In addition. oralternatively. the ice inhibitor may provide a film on the internalportions of the carburetor as it passes in contact therewith preventingan adhesion of ice crystals thereon. Regardless. a two-cycle chainsawengine according to the present invention has a substantially lowertendency towards formation of ice within the interior portions of thecarburetor and a correspondingly lessened tendency towards enginestalling under conditions in which ice may form.

While ice crystals may not be absolutely prevented from forming in thecarburetor. the present invention prevents any ice crystals which mayform from accumulating in a manner which will restrict the flow of fluidthrough the carburetor body. As indicated in FIG. 2. occasional iceparticles 72 may still form in the induction passage 44. However. theeffect of the ice inhibiting means is sufficient to prevent a blockageor to otherwise interfere with the operation of the chain saw. Normally.the small particles of ice which may form notwithstanding the presenceof the ice inhibiting means simply pass into the crankcase of the enginewhere they are almost instantaneously vaporized because of therelatively high temperatures therein.

During operation of the engine. an ice inhibiting means is introducedinto the carburetor by means of the fuel supply system. The iceinhibiting means is mixed with the fuel-lubricating oil mixture of thetwocycle chain saw engine in an amount sufficient to in-' hibit theformation of ice within the carburetor of the engine without. however.appreciably adversely affecting the combustibility or volatility of themixture to be ignited in the engine cylinder which amount. in the caseof hexylene glycol as the ice inhibiting means. may be from about (M to0.2 1 by .volume of the fuel. The ice inhibiting means preferably ispremixed with the lubricating oil (which premix is thereafter mixed withgasoline to provide the combustible mixture which is exploded in theengine cylinder) to facilitate mixing the correct proportionof iceinhibiting means. The concentration of inhibitor in the oil may dependalso upon the ratio of oil to gasoline recommended by the manufacturerof the lubricant. ln the case of hexylene glycol used with oil intendedto be mixed in the proportions of 40:1 1 volume of oil to 40 volumes ofgasoline). the concentration of inhibitor in the oil will range fromabout 4 to 8'4.

it will be appreciated that in utilizing the nov method and apparatusfor inhibiting carburetor icing a chain saw engine according to thepresent inventio certain significant advantages are provided.

in particular. the present invention eliminates a "Cl for structurallycomplex heating apparatus to increa: the temperature of the carburetorwalls or of the intai air to the carburetor as well as the need for anexteril heater or for pre operation modifications which to: increase thecost and complexity of the chain saw c gine. The ice inhibitor of thepresent invention may 1 used when weather or temperature conditions so rquire it and may otherwise not be used. Hence. the is provided a maximumof flexibility of operation wi a minimum of complexity and cost.

Of further significance is the fact that the ice inhil tor may beintroduced into the fuel system of a cha saw engine by means of thelubricating oil. This assur that the proper proportion of ice inhibitoris used to i hibit icing while. at the same time. there is an assuranthat the fuel volatility is not interfered with. Such an a rangementpermits improved operation of a chain s: in a cold environment. and. incommercial situatio such as logging operations. may substantially increathe efficiency of chain saw use.

Thus. it is apparent that there has been provided. accordance with theinvention. a method and apparal for inhibiting icing in the carburetorof a two-cyl chain saw engine that substantially satisfies the obje andadvantages set forth above. Although the pres invention has beendescribed in conjunction with a s cific embodiment it is evident thatmany alternativ modifications. and variations will be apparent to lhtskilled in the art in light of the foregoing disclosure the invention.Accordingly. it is intended that all St alternatives. modifications. andvariations which within the spirit and scope of the invention as deiirin the appended claims be embraced thereby.

What is claimed is:

l. A method for operating a chain saw in an envir ment where ice may beformed in a carburetor me thereof. and wherein said chain saw comprises:

a two-cycle. internal combustion. chain saw engi 45 a cutter chaindrivenly engaged with said chain 1 engine;

reservoir means connected to said chain saw enr and operable to containa combustible lubrica so oil-gasoline mixture for transmittal to acarbon means;

carburetor means for transmitting a volatile mix of air and saidlubricating oil-gasoline mix therethrough for passage to a combustionchan of said chain saw engine; and

said carburetor means having an interior portior eluding aninductionpassage;

said method comprising:

a. storing an ice inhibiting means with a lubric:

oil composition.

b. maintaining a ratio of said ice inhibiting meal said lubricating oilcomposition so as to ensure when said lubricating oil composition isadded predetermined lubricating ratio to said gasoli ratio of iceinhibiting means to gasoline will 1 matically be provided which willsubstantially vent the formation of ice when said gasoli drawn throughsaid induction passage with ai temperature of less than about 40F andhaving a relative humidity of greater than about 50%,

. concurrently mixing said lubricating oil composid. providing. in saidreservoir means. said combustible lubricating oil-gasoline mixturecontaining an ice inhibiting means mixed therewith and operable tosubstantially prevent the formation of ice within said induction passageof said carburetor means during operation of said chain saw engine in anenvironment where ice may be formed in said carburetor means and wheresaid mixture is drawn through said induction passage with air at atemperature of less than about 40F and having a relative humiditygreater than about 50%:

. operating said chain saw engine to pass said combustible mixturethrough said carburetor means of said chain saw engine and therebyintroduce said 8 ice inhibiting means into said induction passage ofsaid chain saw engine to substantially inhibit a formation of icetherein and prevent an ice blockage in said induction passage when saidchain saw engine is operated in an environment where ice may be formedin said carburetor means. and where said mixture is drawn through saidinduction pas- I sage with air at a temperature of less than about 40Fand having a relative humidity greater than about 40%;

. said combustible lubricating oil-gasoline mixture.

containing said ice inhibiting means. being contained within saidreservoir means during said operation of said chain saw while beingsubject to chain saw operation-induced vibration;

g. said volatile mixture of air and lubricating oilgasoline mixturebeing transmitted through said induetion passage of said chain sawengine carburetor means with said ice inhibiting means while saidinduction passage is subject to said chain saw operation-inducedvibration; and

b. said volatile mixture of air lubricating oil-gasoline mixture.including said ice inhibiting means. being transmitted from saidinduction passage through a crank case of said chain saw engine prior tocombustion of said volatile mixture in said combustion chamber ofsaidchain saw engine.

i l i i i

1. A method for operating a chain saw in an environment where ice may beformed in a carburetor means thereof, and wherein said chain sawcomprises: a two-cycle, internal combustion, chain saw engine; a cutterchain drivenly engaged with said chain saw engine; reservoir meansconnected to said chain saw engine and operable to contain a combustiblelubricating oil-gasoline mixture for transmittal to a carburetor means;carburetor means for transmitting a volatile mixture of air and saidlubricating oil-gasoline mixture therethrough for passage to acombustion chamber of said chain saw engine; and said carburetor meanshaving an interior portion including an induction passage; said methodcomprising: a. storing an ice inhibiting means with a lubricating oilcomposition, b. maintaining a ratio of said ice inhibiting means to saidlubricating oil composition so as to ensure that when said lubricatingoil composition is added at a predetermined lubricating ratio to saidgasoline, a ratio of ice inhibiting means to gasoline will automaticallybe provided which will substantially prevent the formation of ice whensaid gasoline is drawn through said induction passage with air at atemperature of less than about 40*F and having a relative humidity ofgreater than about 50%, c. concurrently mixing said lubricating oilcomposition and ice inhibiting means with gasoline to provide acombustible lubricating oil-gasoline mixture containining an iceinhibiting means mixed therewith, and simultaneously i. condition saidgasoline for effective lubrication and combustion in said two-cycle,internal combustion chain saw engine, and ii. condition said gasoline toprevent the formation of ice when said gasoline is drawn through saidinduction passage with air at a temperature of less than about 40*F andhaving a relative humidity of greater than about 50%, d. providing, insaid reservoir means, said combustible lubricating oil-gasoline mixturecontaining an ice inhibiting means mixed therewith and operable tosubstantially prevent the formation of ice within said induction passageof said carburetor means during operation of said chain saw engine in anenvironment where ice may be formed in said carburetor means and wheresaid mixture is drawn through said induction passage with air at atemperature of less than about 40*F and having a relative humiditygreater than about 50%; e. operating said chain saw engine to pass saidcombustible mixture through said carburetor means of said chain sawengine and thereby introduce said ice inhibiting means into saidinduction passage of said chain saw engine to substantially inhibit aformation of ice therein and prevent an ice blockage in said inductionpassage when said chain saw engine is operated in an environment whereice may be formed in said carburetor means, and where said mixture isdrawn through said induction passage with air at a temperature of lessthan about 40*F and having a relative humidity greater than about 40%;f. said combustible lubricating oil-gasoline mixture, containing saidice inhibiting means, being contained within said reservoir means duringsaid operation of said chain saw while being subject to chain sawoperation-induced vibration; g. said volatile mixture of air andlubricating oil-gasoline mixture being transmitted Through saidinduction passage of said chain saw engine carburetor means with saidice inhibiting means while said induction passage is subject to saidchain saw operation-induced vibration; and h. said volatile mixture ofair lubricating oil-gasoline mixture, including said ice inhibitingmeans, being transmitted from said induction passage through a crankcase of said chain saw engine prior to combustion of said volatilemixture in said combustion chamber of said chain saw engine.